docs: def make_coroutine_from_tree(tree, filename="<aexec>", symbol="single",
                               local={}):
      """Make a coroutine from a tree structure."""
      dct = {}
      tree.body[0].args.args = list(map(make_arg, local))
      exec(compile(tree, filename, symbol), dct)
      return asyncio.coroutine(dct[CORO_NAME])(**local)